Accumulated Other Comprehensive Loss - Components of and Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Accumulated Other Comprehensive Income
Balance at beginning of period	$ (10,893)	$ (11,635)
Other comprehensive loss before reclassifications	(387)	1,340
Amounts reclassified from accumulated other comprehensive loss, net of tax of $(1.9 million)	5,772	154
Amounts reclassified from accumulated other comprehensive loss, tax	(1,900)	(100)
Net current period other comprehensive income (loss), net of tax	5,385	1,494
Accumulated other comprehensive (loss) income	(5,508)	(10,141)
Unrecognized pension and postretirement benefits
Accumulated Other Comprehensive Income
Balance at beginning of period	(11,597)	(10,495)
Other comprehensive loss before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive loss, net of tax of $(1.9 million)	5,772	154
Net current period other comprehensive income (loss), net of tax	5,772	154
Accumulated other comprehensive (loss) income	(5,825)	(10,341)
Foreign currency
Accumulated Other Comprehensive Income
Balance at beginning of period	704	(1,140)
Other comprehensive loss before reclassifications	(387)	1,340
Amounts reclassified from accumulated other comprehensive loss, net of tax of $(1.9 million)	0	0
Net current period other comprehensive income (loss), net of tax	(387)	1,340
Accumulated other comprehensive (loss) income	$ 317	$ 200